How To Select Busbar Cross Section

1. Try one of these, or refer to National Electrical Code.
2. Ask someone you know who is smart.
3. busbar size calculation
   
4. BusBarAmpacity
   
5. Busbar Design...
6. how to calculate the BusBar size?

.....or these:

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=busbar%20sizing&order=asc

- one of CR4's favourite topics (apart from cable sizing, and cast iron bath demolition and disposal).

Don't forget the other world famous topic."My Chevy Cavilier won't start, why is that?"

"Piston broke"?

"Yeah. As always. But why don't my motor start?

Please take the current density in the copper Bus bar as:

• 1000Amps/Inch²
• b. 1.55Amps/mm² or 1.6Amps/mm²

The above are practical values. Based on the Amps, Calculate the Bus bar width & dept that are suitable to you.

Current density of busbar may only be used in thumb rule calculation.

In detailed calculation you need to check thermal withstand, electro dynamic withstand even short time withstand current when fault occur. Check this pdf link study pp 21 http://www.engineering.schneider-electric.dk/Attachments/ed/guide/mv_design_guide_design_rules.pdf

Calculating cross section also not enough. Consider 100mm^2,for which you can select either 10x10 or 20x5 and so on. The surface area is different for different sizes,which influences radiation of heat. Also emissivity of surface to be considered.

In one of the posting you had requested about electrical programs to be written in macro for excel.One typical example is selection of Bus bars sizes depending on the inputs like , thermal current,short circuit current,temperature rise and material (aluminium/copper),ambient temperature.

The calculations done by an average person may not be accurate. It depends on properties of material used by different manufacturers. The local supplier or agent should help.

what is the system voltage?

what is the ambient temperature?

what is the ingress protection level of your enclosure (if any)?

is there any forced draft ventilation?

what is the orientation geometrical disposition of the busbar inside the enclosure?

what is the length of busbar?

is it fed from one end?

or is it fed somewhere along its length?

are there any tapped off loads at intervals along the length?

what is the air volume of the enclosure?

what is the system fault level?

is this an ac system of is it dc?

are any harmonics present if it is an ac system?

if yes to harmonics then do you have a predicted spectrum?

what is the power factor of your load?

how much temperature rise can you permit for safe operation?

is the loading cyclic / periodic or continuous?

do you have a good maintenance team for predictive and preventive maintenance for joints?

is the atmosphere corrosive? and humid?

can you write down and place before yourself the answers these questions?

or would you rather just adopt a very safe current density and assume that you are thermally safe under worst case scenario projections?

of course the supports have to be selected and designed too but that is not your query right now . . .

http://cr4.globalspec.com/thread/56420#comment587271

http://www.electricianmath.com/neccalculations/busbarampacity.htm

http://www.schneider-electric.com/documents/technical-publications/en/shared/electrical-engineering/electrical-know-how/low-voltage-minus-1kv/ect158.pdf

http://www.copperinfo.co.uk/busbars/pub22-copper-for-busbars/sec6.htm

http://cr4.globalspec.com/thread/56152

http://www.scribd.com/doc/60189407/Busbar-Calculation

What I gave is the the hint of simple calculation of Bus bar size.

• Rating of the Voltage make the insulation on it or separation from one phase bus bar to other phase bus bar not on the current density
• Bus bar rating is natural air cooled
• As the above suggestions such harmonics, single feeding and so on so forth are based on case to case
• Please refer the world famous Bus Duct supplier or manufacturers catalogues you will understand what i said.